CODEWITHSUNDEEP
javac++protocol-buffers
Gunwant
Gunwant

Reputation: 979

Convert the byte array to java types

I have a very specific requirement. I have a java application, where I have to convert byte array in to message having java types like int, String. The structure of the message is defined in c++ as below - 

struct SMSMessage{ 
int    id;        
std::string name;       
std::string source;     

std::string destination;
std::string timestamp;  
int         type;       
int         status;     
std::string message;    
int         mesg_type;   
int         mesg_sub_type; };

What I receive in my java application is the byte array. I don't know wheather c++ application is using proto buffers or any other way to convert in to a byte array. But, if I parse the array using byte by byte, I could get the values. For example -

ByteBuffer.wrap(Arrays.copyOfRange(byteArray, 0, 4)).getInt();
//byteArray -- reference to the incoming byte array
// 0, 4-- range of bytes for integer type

This line will return correct id value (First property in structure is int).

My question are - If I write the proto for this structure, could I be able to parse this message in to java ?

Is there any other way to convert the byte array to java types ?(not using library like google protobuf )

Upvotes: 0

Views: 844

Answers (2)

ARau
ARau

Reputation: 489

You may be able to use the open source javolution library specifically take a look at the Struct class which provides some support for directly mapping C structs to Java types.

You will encounter problems mapping the std::string type as the length of the string is not known beforehand. You will need to read this in as a byte stream until you find the null terminator which signifies the end of a string.

Upvotes: 0

RisuRyu
RisuRyu

Reputation: 134

I'am not sure if you can convert it directly into a java structure but i guess it is not so easy possible. Also if it works you can't be sure that the size of the Datatypes are the same. If you run the C++ Application and the Java Application on a different Machine with a different architecture it can be different sizes.

So in my opinion the best option would be you write it first into a json or xml file and read it back from the other application.

If you want do it like you already wrote, then maybe you should sort the c++ struct by types. So you can better use a loop. Like, i have 5 times a integer of 4 bytes and 5 times a string with X Bytes.

mfg

Upvotes: 1

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